As a popular technique for viewing 3D images, there is currently a technique by which a viewer views images of two viewpoints that are alternately displayed. In viewing the images of two viewpoints, the viewer wears glasses that open the shutter for the left eye when one of the images of two viewpoints is displayed, and open the shutter for the right eye when the other one of the images is displayed (hereinafter referred to as the glasses-involving technique).
However, with such a glasses-involving technique, a viewer needs to purchase glasses as well as a 3D image display device, and this reduces the viewer's purchasing interest. Also, the need to wear glasses at the time of viewing is troublesome for a viewer. Therefore, there is an increasing demand for a viewing technique by which a viewer can view 3D images without glasses (hereinafter referred to as a glasses-free technique).
By the glasses-free technique, images of three or more viewpoints are displayed in such a manner that the viewable angle varies at the respective viewpoints, and the viewer can view a 3D image without glasses by seeing each image of any two viewpoints with the right and left eyes.
A decoding device that provides glasses-free viewing generates and displays images of three or more viewpoints from images of two viewpoints, for example (three or more viewpoints will be hereinafter referred to as “multi-view”). Specifically, an encoding device determines parallax (depth) values of images of two viewpoints, and transmits parallax images (depth images) representing the parallax values in the form of luminance values or the like to a decoding device. The decoding device generates multi-view parallax images by performing a warping operation on the received parallax images of the images of the two viewpoints. Using the multi-view parallax images, the decoding device generates multi-view images by performing a warping operation on the images of the two viewpoints, and combines the multi-view images for display.
It should be noted that a warping operation is an operation to change the parallax value (or pixel value) of each pixel in a parallax image (or image) of a predetermined viewpoint to the parallax value (or pixel value) of the pixel corresponding to the pixel in a parallax image (or an image) of a virtual viewpoint.
Examples of conventional image encoding techniques include AVC (Advanced Video Coding) and MVC (Multiview Video Coding). Further, there is a suggested technique for encoding multi-view images (see Patent Document 1, for example).